Fluid filled cable



April c. A. PIERCY 2,196,0 6

FLUID FILLED CABLE Filed Aug. 6, 1936 Inventor:

Carl A Hero Attorney.

Patented Apr. 2, 1940 FLUID FILLED CABLE Carl A. Piercy, Ballston Lake,N. Y., assignor to General Electric Company, a corporation of New YorkApplication August 6, 1936, Serial No. 94,621

6 Claims.

In the manufacture of fluid filled cable of the single conductor type,it is desirable in order to reduce the overall diameter of the cable tocompact the strandsas fully as possible. As a result of this, the usualspaces between strands are practically non-existent with the result thatradial movement of the fluid between the strands is largely or whollyprevented. It is also desirable in very large conductors to divide thetotal cross-sectional area into segments, all operating at the samepotential, so as to reduce eddy current and other losses in theconductor itself. After the segments have been assembled in a socalledclosing machine to form a cable, an insuld lating covering comprisingmany layers of paper or other fibrous insulation is tightly applied. Inorder to form a channel for the impregnating fluid, such as oil, anaxially extending opening is provided. Because the segments are alloperating at the same potential, they need not for that reason beinsulated one from the other, and because the spaces which exist betweenstrands where round wires are used are no longer present due to thecompacting, the problem is.presented u of providing suitable means forconveying the. oil or other fluid contained in the channel or core tothe body of pervious insulation surrounding the conductor without theapplication of an abnormally high pressure .on the fluid which would be30 injurious to the sheath.

The object of my invention is the provision of an improved singleconductor cable of the fluid filled type having channel means locatedbetween adjacent segments adequate to convey fluid from a the core orcentral channel into the surrounding insulation so that the latter willbe fully impregnated under all operating conditions.

For a consideration of what I believe to be novel and my invention,attention is directed to o the accompanying description and the claimsappended thereto.

In the drawing which is illustrative of my in vention, Fig. 1 is across-section of a multi-segment single conductor cable; Fig. 2 is apartial section of a modified form of my invention; Fig. 3 is a detailview of a spacer located between adjacent segments; Fig. 4 is a furthermodification in which. special channel means are formed in the strandsof the conductors; Fig. 5 is a detail 50 view of the channel means ofFig. 4, and Fig. 6

illustrates a modified form of the partitions illustrated in Fig. 2.

Referring to Fig. 1, 5 indicates segments of the same conductor of whichsix are shown. The uninsulated strands 8 of each segment are compactedto such an extent that as a practical matter, there are no open spacesbetween strands through which fluid could pass from the center channel Ito the layers of permeable insulation 8 surrounding them. To reducelosses in the 5 cable due to so-called proximity eflect, the wires orstrands are so arranged that each strand instead of occupying the sameradial position throughout the cable is changed by a definite plan,flrst appearing as a bottom or inner strand m and later as an outerstrand and then as an inner strand, etc. There is nothing new in thisfeature, it being old in the cable art. In the center of the assembly isa core 9 made of narrow metal stock wound in the form of a coiledextension spring with spaces between turns to permit oil to pass. Thiscore is primarily of use in assembling the segments ina closing. machineto the end that each segment will occupy its proper radial position withrespect to the axis. Under certain conditions, the use of this core as aguiding or centering means may be omitted.

Because the segments are operating at the same potential, they do notfor that reason need to be insulated from each other but in order toattain the advantages of the strand relation previously referred to, thesegments should be insulated from each other. Since the segments allcarry current at the same voltage, the insulation between them 'need notbe very thick. It is the 3 insulation 8 which insulates the conductorsfrom ground. In order to carry fluid such as thin degasified oil fromthe center channel 1 to 'the surrounding body or belt of insulation andvice versa, thin bodies of permeable material ID are 35 located betweensegments. These bodies which are thin may be wrapped entirely aroundeach segment or they may be located only between adjacent surfaces. In aradial direction, the

bodies should extend between the segments from o the center channel toany permeable covering over said segments. As illustrated in thisfigure.

the bodiesextend entirely around each segment and in each case thecovering so applied is of the order of 14 mils in thickness. However,when 5 the segments are assembled in the closing machine, the pressureexerted thereby on the bodies or coverings will compress them to say 20mils total between each two segments. A metal binding tape i2 arrangedwith rather widely spaced turns is desirable to prevent the segmentsfrom spreading or bird-caging when the cable is bent as in reeling andunreeling. Because it is im-- portant to prevent short circuiting of thesegments andthereby nullify to an extent the advantages ofsegmentalconst-ruction, one or two layers of permeable material I 3,such as paper, are wound over the segments and under the binding tape.The outer corners of each segment are slightly rounded and in theapproximately triangular spaces thus formed, there are .or may be laidsoft cotton, paper or equivalent cord H for the purpose of making theassembly circular in form and at the same time preventing concentrationof electrical stresses in said spaces. Surrounding the binding-tape is abody 8 of permeable insulation in the form of relatively narrow tapes orribbons applied layer by layer in such manner that the joint betweenturns on one layer is covered by the tape of the next outer layer.Enclosing the body of insulation is a lead sheath N3 of ordinaryconstruction. As a result of the construction described, the radial orpartition portions of the bodies l0 serve to convey by capillary actionoil from the center channel to the surrounding body of insulation 8 andmaintain it in a fully impregnated condition.

In those cases where a more rapid or freer transfer of fluid such asthin degasified oil between the channel and the surrounding body 8 isdesired, the construction of Fig. 2 may advantageously be employed. Inthis case, the segments are not initially provided with a covering ofany sort but are left bare just as they come from the compacting rolls.To simplify the i1- lustration the individual strands of which theconductor is composed are not shown but in practice they will resemblethose of Fig. 1. In order to transfer fluid between the center channel Tand the body 8, non-conducting partitions or spacing strips I! areplaced radially between adjacent faces of the segments and held in suchpositions by the sidewise pressure of the segments. These may be madefrom fibre or equivalent material and are inserted in the form oflongitudinal strips as the segments pass through the closing machine.Each of the strips is provided with shallow grooves I8 in one or both ofthe side faces so that when the segments are assembled, the grooves formnumerous passages or auxiliary channels for the transfer of 011, saidauxiliary channels being fed in parallel from the main channel. Asshown, the grooves are radially disposed but they may be arrangeddiagonally as shown in Fig. 6. However they are made, they should allreceive oil in parallel from the central channel and convey it to andfrom the surrounding insulation 8. The lower edges of the strips shouldhave access to the oil in the channel and the outer ends shouldterminate at some point near the layer or layers of paper under thebinding tape. The said outer ends desirably terminate in thesubstantially triangular spaces formed by the rounded corners of thesegments. The arrangement of the binding band, insulation 8 and sheathis the same as described in connection with Fig. 1. In this instance,instead of relying upon capillary action to convey the fluid between thecentral channel and the insulation, the pressure exerted on the fluid inthe main or central channel suffices for the purpose.

In Figs. 4 and 5, a generally similar arrangement is provided butdiffering therefrom in that the strips or partitions I! are smooth onboth sides and the radial grooves or auxiliary passages l9 are formed inthe surfaces of the conductor segments on opposite sides of the strips.It is advantageous to make the partitions between segments as thin aspossible so as to reduce the overall diameter of the cable. By makingthe grooves in the conductors instead of in the partitions, it followsthat this advantage is attained. The use of thin partitions also reducesthe losses in the conductor. The grooves I9 can readily be formed by thesame dies or rolls which compact the strands by proper shaping of therolls forming the sides of the segment.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A fluid filled cable comprising segmental bodies of densely compactedstrands of bare wire without appreciable strand spaces, the bodiesoperating at the same potential and forming a single conductor ofcylindrical form, a member located within and engaging the innersurfaces of the segments which acts as a centering means for thesegments and with them defines an unrestricted central channel forfluid, a covering of dense permeable insulation for the segments, radialpartitions of non-conducting material located between'the side faces ofadjacent segments and held under compression by said segments, thepartitions serving as segmental spacers and also having grooves servingas means for conveying fluid between the central channel and theinsulation, and an impermeable sheath surrounding the insulation forconfining the fluid.

2. A fluid filled cable comprising segmental bodies of densely compactedstrands of bare wire without appreciable strand spaces arranged to forma single conductor of cylindrical form and defining a central channelfor fluid, there being radial grooves formed in certain of the sidefaces of the segmental bodies forming parallel fluid passagescommunicating with the central chan nel, a dense body of permeableinsulation surrounding the segments, non-conducting radial partitionshaving smooth side surfaces located between the side faces of each pairof segments, certain of said faces defining walls of the grooves in thesegments, and an impermeable sheath surrounding the insulation toconfine the fluid.

3. A fluid filled cable comprising segmental bodies of densely compactedstrands of bare wire without appreciable strand spaces assembled to forma single conductor of cylindrical form and defining a free open channelfilled with liquid insulation under positive pressure, athin metallicbinding tape exerting inward pressure on the segmental bodiesfor firmlyholding the segmental bodies and preventing them from separating, a bodyof non-conducting material located between the peripheral surfaces ofthe bare conductors and the tape of suflicient thickness to preventshort circuiting of the segments but not to insulate them from ground, adense body of permeable insulation arranged in layers and surroundingthe tape for insulating the segments from ground, partitions ofnon-conducting material between the adjacent faces of the segments heldin firm contact therewith and occupying radial positions, the saidpartitions and one of each 1|) sulation for confining the fiuid.

5. A liquid filled cable comprising segmental bodies of stranded wirescompacted to such an extent as to prevent free radial movement of liquidbetween the strands, the segmental bodies 15 operating at the samepotential, a central open channel defined by the inner portions of theseg- ,mental bodies containing liquid insulation under positivepressure, a body of dense permeable insulation common to the segmentalbodies and M surrounding them, radially disposed partitions locatedbetween adjacent faces of the segmental bodies and firmly held in theirrespective positions by the sidewise pressure exerted thereon by thebodies, each partition and one of the adjacent 25 side walls of thebodies defining free passages open at both ends and arranged to receiveliquid in parallel at their inner ends from the channel and freely toconvey it to and from the surrounding permeable insulation, and animpermeable 6. A liquid filled cable comprising bare segmental bodies,each composed of wires stranded to reduce losses due to proximityeffects and as sembled to form a single conductor of cylindrical form,the segments operating at the same potential, a central opening channelcontaining liquid insulation under positive pressure, the wires being sodensely compacted as practically to shut off the radial passage ofliquid insulation between the open channel and the periphery oftheassembled segmental bodies, a thin metallic binding tape exerting inwardpressure on the segmental bodies for firmly holding them in theirassembled positions, non-conducting material 10- cated between thebinding tape and the bodies to prevent short circuiting thereof by theband, a dense body of permeable insulation arranged in" layers andsurrounding the tape, radially dis-' posed partitions located betweenadjacent faces of the segmental bodies and held in their respectivepositions by the sidewise pressure exerted thereon by the bodies, eachpartition and one 80 sheath surrounding the insulation for confining theliquid. w

of the segmental bodies defining free passages open at both endsarranged to receive liquid in parallel from the channel and convey it toand from the surrounding permeable insulation, and an impermeable sheathsurrounding the insulation for confining the liquid.

CARL A. PIERCY. 80

